1. Field of the Invention
The present invention relates to novel composites of bioactive materials and certain functionalized polyaryl polymers and methods for their preparation, as well as articles of manufacture constructed therefrom.
2. Description of the Prior Art
There has long existed a need for composite or hybrid biomedical articles which combine the structural properties of organic polymers and the biological properties of bioactive inorganic materials. Such materials often take the form of bulk polymers in which are interspersed bioactive particles or fibers. Due to the inherent mutual incompatibility of the great majority of organic polymers and inorganic materials, it has proven extremely difficult to construct composites or hybrids thereof wherein the instability at the interface between the incompatible organic and inorganic phases does not result in highly disadvantageous structural defects in articles constructed therefrom which drastically limit their effectiveness.
Previous efforts to eliminate or reduce this interfacial instability have proven largely unsuccessful. One approach to improving interfacial strength focussed on enhancing wetting of the interfacial surfaces of the incompatible polymers and inorganic fillers. For example, silane coupling agents such as amino triethoxysilane resulted in an increase of the elastic modulus of polymer/glass composites which enabled higher levels of stress transfer through the interface. The overall strength of the composites was also enhanced by using these coupling agents; however, the strain at failure of the thus-treated composites decreased when compared with composites prepared without the coupling agents. This reduction in strain at failure has been interpreted as resulting in a reduction of the toughness of the silane coupled composition.
The interface plays a very important role in the performance of composites. The interface is responsible for transferring stress from the matrix to the fibers/fillers and, therefore, high levels of matrix reinforcement are intimately related to the behavior of the interface as a stress transfer agent. Adhesion between reinforcing agents and matrix is the main interfacial property that should be maximized in order to improve stress transference. Many ways to improve adhesion in polymer composites are currently being investigated, i.e., chemical modification of surfaces such as by the use of the above-described silane coupling agent, and physical modifications such as plasma treatment organic/inorganic composites are polymer-ceramic composites in which the components are combined at the nanometer level. Thus, organic/inorganic composites can have tailorable properties that range within the entire spectrum of properties between ceramics and polymers. organic/inorganic composites as interfacial modifiers are the natural way to reduce both the chemical and mechanical abruptness of the interface in polymer composites reinforced with ceramic fibers. The use of organic/inorganic composites as interfacial modifiers allows the production of an interphase with a gradient of mechanical properties and chemical structure that can improve both chemical interactions and stress transfer. An interphase with a gradient of elastic modulus, for example, minimizes the abruptness of the interface in composites, thereby enabling higher levels of transfer stress than the conventional interface with discontinuous properties thereacross.
Inorganic-organic hybrids have been studied for some time as a way to produce composites with nanophases and diffuse interface. These types of inorganic-organic hybrids are the natural choice for making tailorable interphases in conventional fiber/particle reinforced composites since their structure and composition can be altered to better match the requirements for high levels of adhesion and toughness of the interface. By combining the type of polymer used in the matrix with the nanosized silicate phase, a cross-linked structure that can resemble both the matrix and the reinforcement of the composite can be achieved. In this case, stress transfer can be optimized by breaking the abruptness of the conventional interface in terms of mechanical properties. Thus, the inorganic-organic hybrid, acting as an interfacial agent, would have an elastic modulus between values of the matrix and fiber/particle.
It is an object of the invention to provide novel organic/inorganic composites having greatly enhanced interfacial stability.
The above and other objects are realized by the present invention, one embodiment of which relates to a composition of matter: a mixture of an inorganic material and an organic material; the organic material comprising a silane functionalized polyaromatic polymer and the inorganic material comprising a network of moieties reactive with the silane groups of the organic material under conditions which do not substantially destabilize the organic and inorganic materials to provide a covalent bond between the moieties and the silane groups.
A further embodiment of the invention concerns the composite formed by reacting the above-described mixture to form a composite comprising the inorganic material covalently bonded to the organic material.
Another embodiment of the invention comprises, as a composition of matter, an organic-inorganic composite comprising a silane functionalized polyaromatic polymer bonded via the silane groups to an inorganic material comprising a network of moieties reactive with the silane groups by a condensation reaction to form covalent bonds therebetween.
Yet another embodiment of the invention relates to a method of forming a composite of an inorganic material and an organic material comprising reacting the above-described mixture to form a composite comprising the inorganic material covalently bonded to the organic material.
An additional embodiment of the invention comprises articles of manufacture constructed of the above-described compositions.